[KJ] fixing compile warnings

[KJ] fixing compile warnings

[David Farning]

I am working my way through the compile warnings in /fs

I have come across this set of warning

fs/jfs/jfs_txnmgr.c: In function ‘txCommit’:
fs/jfs/jfs_txnmgr.c:1922: warning: ‘pxd.addr2’ may be used uninitialized
in this function
fs/jfs/jfs_txnmgr.c:1922: warning: ‘pxd.addr1’ may be used uninitialized
in this function
fs/jfs/jfs_txnmgr.c:1922: warning: ‘pxd.len’ may be used uninitialized
in this function

The relevant code is as follows

	if (tlck->type & tlckTRUNCATE) {
		pxd_t pxd;	/* truncated extent of xad */
		int twm;

pxd_t is defined as follows


 96 typedef struct {
 97         unsigned len:24;
 98         unsigned addr1:8;
 99         __le32 addr2;
100 } pxd_t;

What is the proper (kernel) way to initialize pxd_t in jfs_txnmgr.c to
silence the warnings?

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Re: [KJ] fixing compile warnings

[Tony Breeds]

On Sun, Sep 10, 2006 at 09:30:31PM -0500, David Farning wrote:
> I am working my way through the compile warnings in /fs
> 
> I have come across this set of warning
> 
> fs/jfs/jfs_txnmgr.c: In function ???txCommit???:
> fs/jfs/jfs_txnmgr.c:1922: warning: ???pxd.addr2??? may be used uninitialized
> in this function
> fs/jfs/jfs_txnmgr.c:1922: warning: ???pxd.addr1??? may be used uninitialized
> in this function
> fs/jfs/jfs_txnmgr.c:1922: warning: ???pxd.len??? may be used uninitialized
> in this function

If I read xtLog() correctly there is no way pxd can be used with out
being initialised.

The code goes something like:
xtLog()
{
...
	if (tlck->type & tlckTRUNCATE) {
		pxd_t pxd;	/* truncated extent of xad */
		....
		if (twm = next - 1) {
			...
			pxd = pxdlock->pxd;	/* save to format maplock */
			...
		}
		...
		if (twm = next - 1) {
			...
			pxdlock->pxd = pxd;
			...
		}
	}
...
}

With no changes to twm or next between the 2 access.
 
> What is the proper (kernel) way to initialize pxd_t in jfs_txnmgr.c to
> silence the warnings?

I guess you could do something like:

---
        if (tlck->type & tlckTRUNCATE) {
-               pxd_t pxd;      /* truncated extent of xad */
+               /* truncated extent of xad */
+               pxd_t pxd = {0, 0, 0};  /* FIXME: shutup GCC */
                int twm;
---

But I don't really think that's acceptable.

However, in looking at this question I found a shadow variable, I think the
patch below is a reasonable fix.


From: Tony Breeds <tony@bakeyournoodle.com>

Remove shadow variable from fs/jfs/jfs_txnmgr.c:xtLog()

Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>

---

 fs/jfs/jfs_txnmgr.c |    2 --
---

--- a/fs/jfs/jfs_txnmgr.c
+++ b/fs/jfs/jfs_txnmgr.c
@@ -2026,8 +2026,6 @@ static void xtLog(struct jfs_log * log, 
                 * truncate entry XAD[twm = next - 1]:
                 */
                if (twm = next - 1) {
-                       struct pxd_lock *pxdlock;
-
                        /* format a maplock for txUpdateMap() to update bmap
                         * to free truncated delta extent of the truncated
                         * entry XAD[next - 1];

---

Yours Tony

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